This world is quite different from our world. Even though it is Earth there are some major changes.
It all started on 2020 in this world something happened which ended up destroying 80% of the population. This also caused a lot of the technology to dissapear.
The events take place after 300 years, due to the sheer destruction all the remaining people in power made a decision to halt the movement of technology and focused on sustaining humanity.
And in around 200 years the world had recovered and now there were about 9 billion people.
And technology started making movements, the problem was most of the technology was decimated, so they had to start all over again. The current technology is advanced than ours but not by a large margin.
Also most of Europe was declared a top secret zone.